“…Also, the port injection of DEE helps it to 568 mix properly with the air-biogas mixture and forms many ignition 569 centers in the combustion chamber and gives a lower CO emission 570 [5,35,52]. NO emission with the DEE injection is attributed to the higher oxy-612 gen enrichment (from both DEE and KME) and a more complete 613 combustion may give higher thermal NO due to high combustion 614 temperature [5,35,37,56]. The NO emission for BDFM24.5/DEE2, 615 BDFM24.5/DEE4, and BDFM24.5/DEE6 is about 13.5%, 10.9%, and 616 5.7% lower than that of KME, at full load operation respectively.…”